Grinding machine



Dec. 7, 1954 E. G, ROEHM 2,696,066

GRINDING MACHINE Filed July 9, 1953 3 Sheets-Sheet 1 INVENTOR.

E/W/N G. ROEHM TTORNEYS.

Dec. 7, 1954 E. G. ROEHM 2,696,065

GRINDING MACHINE Filed July 9, 1953 3 Sheets-Sheet 2 56 f7 EL-Lg. E'

67 68 A INVENToR. 2 ERw/N 6'. RQEHM BY WM/mun A7 TORNEYS.

Dec. 7, 1954 E. s. ncbi-:HM

GRINDING MACHINE Filed July 9, 1953 3 Sheets-Sheet 3 EN TOR ERW/N G. ROEHM TTOHNEYS.

United States Patent O GRINDING MACHINE Erwin Roehm, Norwood, Ohio, assignor to The Cinclnnati Milling Machine Co., Cincinnati, Ohio, a corporation of Ohio Application July 9, 1953, Serial No. 366,947

9 Claims. (Cl. 51-100) :This invention relates to improvements in grinding machines, and relates particularly to a novel and improved machine for performance of form grinding operations.

One of the principal objects of the present invention is the provision of an improved machine, particularly adapted for the grinding of contours or irregular shapes in correspondence with the dictates of a controlling pattern or master. l A further object of the invention is the provision of an improved multiple spindle grinding machine capable of utilization for simultaneously producing a number of duplicate work pieces under control of a pattern which includes means for facilitating the several relative movements of the work pieces and grinding wheels for minimizing the power required for shifting of the parts and for increasing the sensitivity and consequent accuracy of operation of the machine.

A further object of the invention is the provision of a machine tool embodying improved means for supporting a tool spindle for universal movement in a plane with respect to the work piece to be operated upon and in which the various movements in the cutting plane as determined by a tool on the spindle may be readily automatically controlled.

An additional object of the invention is the provision in a machine as above set forth of simplified mechanism for supporting the weight of the spindle carrier and associate parts to facilitate their ready movement and adjustment.

Other objects and advantages of the present invention should be readily apparent by reference to the following specification, considered in conjunction withy the accompanying drawings forming a part thereof, and it is to be understood that any modifications may be made in the exact structural details there shown and described, within the scope of the appended claims, without departing from or exceeding the spirit of the invention.

Figure l is a front elevation of a machine embodying the principles of the present invention.

Figure 2 is a side elevation with a portion of the grinder casing broken away.

Figure 3 is a plan view of the machine.

Figure 4 is a view partially in elevation and partially in section on the line 4 4 of Figure 3, and

Figure 5 is a diagrammatic view of the hydraulic control circuit for the machine.

Figure 6 is a horizontal section of the pattern on line 6-6 of Figure l.

Figure 7 is a horizontal section of a work piece on line 7--7 of Figure l.

In the drawings the numeral 10 designates the bed of a grinding machine having rising at the rear the hollow upstanding column 11 provided with ways 12 for the vertically movable slide 13 which may be moved up and down on the face of the column by any suitable adjusting mechanism. One mechanism for this purpose is particularly illustrated in Figures 2 and 4. Mounted in the column are a pair of spindles 14 and 15 on which are rotatably supported the worm gears 16 and 17 meshing with the worms 18 and 19 on the slide adjusting shaft 20. This shaft is provided with a beveled gear 21, meshing with the bevel gear 22 on shaft 23 which extends forwardly from the column 11 in the housing 24. A pilot wheel 25 is loosely mounted on the forward end of the shaft and can be coupled with the shaft by the clutch structure indicated at 26. Rotation of the pilot wheel in one direction or the other will rotate the worm and thus the gears 1 6 and 17 Connected with these gears are the Arock arms Mice 27 and 28 connected by the links 29 and 30 which are pivoted to the slide 13. Rocking movement of the arms 27 and 28 serves incrementally to raise or lower the slide.

At its ends the slide is provided with the trunnions 31 and 32 on which are pivoted the toggle links 33 and 34. A second pair of links 37 and 38 are pivoted to the links 33 and 34 by the pins 35 and 36 at one end, and their opposite ends are connected by the pivots 39 and 40 to the tool carrier plate 41. A rod 42 connects the pivots 35 and 36 to maintain the same in preselected spacing so that the combination of the several toggle links and rod 42 form a parallel motion connection intervening the vertical movable slide 13 and the tool carrier plate 41.

Mounted on the tool carrier plate 41 are a plurality of brackets 43, each supporting a self-contained motor driven spindle unit comprising a motor 44 for driving spindle 4S carrying the small diameter grinding wheel 46 for operation on a work piece 47 secured in position on the bed of the machine as by the clamp screw 48,

To provide for free vertical adjusting movement of the slide 13 and at the same time effect a counterbalancing of the slide 13 and the tool carrier 41 so that the parts may readily be adjusted in unison and the toggle links serve primarily as a positioning support relieved of the main portion of the weight of the carrier 41 and associate parts, use is made of the counterbalance weights 49. These have been illustrated as two in number contained within the hollow column 11 and each provided with a pulley 5@ around which is passed a supporting cable 51 having one end extending over the idlers 52 and 53 and secured in the eye 54 carried by the slide 13. The opposite end of the cable 51 extends over the idler 55 and idler 56 at the front of the column extension 57 and is, in turn, secured to the eye 53 carried by plate 41. As shown, there are employed two sets of these cables and idlers suitably spaced apart as respects the direction of longitudinal extent of the vertical slide and the spindle carrier so that they exert a balancing or stabilizing elfect as to the horizontal position of the parts, preventing binding of the slide on the ways 12 and at the same time exert an equalized upward force on corresponding portions of the slide 13 and carrier 41. By this construction the carrier 41 is supported for relatively free swinging movement by the linkages 33, 37, and 34, 38 and is capable of being easily moved'in a forward and back direction, varying the separation between the members 41 and 13, or in a longitudinal direction parallel with the member 13 or in any combination of such movements so that the spindles 45 may be shifted in an ambulatory path about the respective work pieces 47. j v

In the present instance the work pieces have been shown as turbine blades which may be of carbide or other dithcult to machine material in which it is necessary that the various pieces be accurately produced as duplicates to very line tolerances. To enable the movements of the spindle carrier to be accurately controlled, there is mounted on the carrier a pattern holder bracket supporting the pattern 60 which in the particular arrangement shown is indicated as beingmounted in a reverse or opposite direction from the mounting of the work piece 47, thus providing a pattern of opposite hand to the work pieces. Mounted on the bed 10 for cooperation with the pattern is a 360 degree tracer head unit 61, which may be of the type shown in detail in Patent 2,332,533, including a tracer finger 62'engageable with the pattern 60. This head is preferably carried by a slide 63 on the bed, permitting longitudinal adjustment to insure proper contact between the tracer iinger and pattern when the several work pieces are correspondingly engaged by the cutters or grinding wheels 46. This tracer unit is of standard conventional construction in which the intermediately pivoted tracer spindle 64 reacts on a valve 65 controlling rotation of motor 66 which, through the diagrammatically indicated drive connection 67, operates the rate and direction control cam 68. This cam engages a first plunger 69 on the reversing valve 70 in valve casing 71. It also engages the plunger 72 of the reversing valve 73 in casing 74.

As is conventional, these plungers are phased at a degree angle to each other as respects the contacting' portion of the camso that rotation of the cam imparts successive incremental ladjustments to the valves. A

pump 75 constitutes Va sourceof pressure-Supplyinglactuz..

ating medium to the conduit76 which has a first branch conduit 77 controlled by the valve 65 in the valve bushing, 77. A. second ,bran ch.,conduit,.78, extends. tol thevalve casing 71. The position `of the valve 70,r determines theconnection of `the actuatingrnediumto .either conduit 79 or 80,'the'se conduits; extendinggtoopposite ends` of the in andout..movement control' cylinder S1 having intermediately disposed. therein piston 82 kon rod 83. Movementsof the yvalve 70 will. connect the pres-- sure conduit V78-with .oneof the,conduits 79 or 80 and will. simultaneously connect the. other,ofv said, pair of conduits Withthe .generalreservoir or;.,return conduit system,..thus. determining thendirectionandv extent of movement of piston. 82..

A third branch pressure, conduit. 85,'extends.. to :the valve-casing74. and is coupledby valvev73 with either the conduit. 86..or conduit .87,y This pairofconduits` extends toV oppositeendsof. the ,cylinder.,88.having intermediately disposedthereinthe pistonv89 carried `by pis tonrod 90.

As particularly -illustratedin .Figure 3, the .spindle carrier 41 is provided with a first -guideplate 191having a .slot- 92extending .parallelwith the longitudinal dimension `of the carrierand adapted .to receive .the pin or connection. 93 .onthe forward cndxofthe pistonrod 83.. Due to this linterconnection ofithe parts,v any in orl out movement imparted. tothe piston 82a,willelect.

a .corresponding movement, ofthe; carrier :41 as respects theslide 13 onwhich. thecylinder 81-is vxed;bybolts.94.

The carrier yis provided with .a second guide, platel 95 having a slot 96 `disposed atright angles to ,thedirection of-` extentof slot'92..and-having engaged in this guidek slotvthepin .97 carried by ypiston rodf90.: Cylinder 88 1s secured to the'carrier 13 by bolts 98. Consequently, upon movement. of the1piston `89.1inone direction or thel other. `the cylinder wills remain'rstationary while theconnection between the piston rod90 andthe guide plate 95 will cause a-transverseinovernentY of the carrier 411 inra direction parallel toxtheface `of the. slide 13,.the interengagement kof pin 93 onpiston `rod` 83 .in 4the -slot 92 `permitting-.this relative slidingmovementwhile the pin 93 restrains the spindle carrier against inward orl Correspondingly, when the 'piston 82 1s actuated, the interengagement of pin 97 with guide outward movement.

plate 95 will permit free'movementuofithek member-4l toward or from the .v carrier :13 .-'whilerestraining the parts against any' relative transverse 4movementai Frornzthe 'foregoing it will be.-noted .that ,there-hasbeen provided :pby the; .present l.invention-i t .an improved v simplied contour grinding machine .for accuratequantity production of contouredy parts yin accordance.` with: the.` shape dlctated by a pattern orrmasteninwhich the-tracerl unitfor control of movemennofthefmachine-isfrigidly supported by the:` bed 'of the--rnachine'asi-is thewpower unit, .while .the powersunitsf-ffory electing thefztwo` direc-` tional movements of'fthefgrinding'wheel spi-ndles fwhichjointly ldetermine i the Yorbitali pathof l movement f ,ofi the-l spindles with respect to -the `workt pieceas .dictated-bv the pattern 'engagement of #the ftracerare` supported. by an indexible or feeding slideistationary,onzthev column By such Aconstructionfthe weight and :mass of lthe -movablefparts under-e tracer condtrol is-minimized'and'. reduced `,to a .single spindlewcarriersupported for universal movementdn a plane. .It will-fur.-A ther be noted -that bythefmethod Aor suspensionemplQyed,

during contouring. movements;

an extremely free movement'of the zspin'dle.carrieri'isat4 tained in that themajor-portion@of the:carrier-"weightV is-supported by lthe counterba'la'ncez49 relegating .to :the toggles'33-37 and 34--38=fsubstantially onlycthef-func. tiony of positionable :maintenance:` of the.--:carrier':41 in parallelism Vwithv the Verticalfslide' l13, the fcarrien" being substantially free-:floating onr'the pivot'bearin'gs t for;,th'e toggle'sn and :doing away' with .frictional' resistanceswattendantupon "use of cross slides orthe like,=thus^greatly increasing the sensitivity of the machinef for `slight variances in the resultant direction of movement ot" grinding wheel and worlc=effected by ther-power lshifters 82"..and v89. As shown; eachv toggle link' cornprisesr-an.`

upper-:and lspaced lower portion,1said portions4 cooperating respectively with the upper and lower faces. l01""the` slide.:` and carrier-,.1 maintainingzathe. f carrier inrvertical parallelism with then slide.:

It will further; be; noted :thatgthel :main supportinglor;

vertical slide 13 is counterbalanced to facilitate its free incrementaladjustmentwhichmay bev effected bythe pilot wheel 25 or suitable alternative conventional slide indexing mechanism. In the present instance, the slide has been indicated as provided with the abutment 99 movable between the adjustable dogs 100 for limiting the vertical adjustments of the grinding wheels 46 with respect to the work pieces 47.

Particular attentionis invited tothev position and relationship of the pattern 60 as respects the produced work pieces r47` and their configuration. As illustrated in Figure l, the cutters-46 are at an intermediate position axially or lengthwise of the work pieces 47 determining the axially ytransverse, plane of contour engagement at the moment' between the grinding Wheels or cutters and the work pieces.vv Correspondingly, the tracer contactor 62 is shown at an intermediate point which determines the axially transverse plane of contour engagement utilized at that time between the tracer and-pattern. lt willbeunderstood that as the slide 13 is raised, the cutters and the pattern will move upwardly with respect to the ixedtracen head unit and its tracer finger contactor at 62, while as the slide and the associated cutter carrier is, moved downwardly the -cutters 46 and contactor 62.

willjjapproach to the bases Vrespectively of the work piece andthe pattern. the Ipattern, which is shown as of tapered form, is mounted withV its knarrower -end pointing downwardly, or phasedglSO degrees as respectsthe position of the work rece...

By reference `toFigures 6 4and 7 representing respectivelyA a horizontal` section or section in an axially transverseplaneof thepattern and of the work piece, it will be seenV that the piecesare of symmetricalform but occupy positions on opposite hand or rotated through 180 degreesv one with respect to theother. In other words, the concave surface104 of the pattern controls reproduction `ofthe corresponding surface 103 on the work, and theyconvex surface v102. on the pattern, -the convex surface 101 jon ,the work, yand the thickened rounded end 106- servesasproper guide for a corresponding portion 105L on the work.

Inordinary 360 degrees contouring operations in which the, pattern and-...work are supported as one unit and the.,-.tracer and cutters, asa second. unit, the pattern and work pieceare correspondingly, positioned. In the present,ns t,ance,vhowever, thepattern and `cutters are mounted. `ina .-ixed relationship .while the vtracer .and work, pieces.,,arerlikewise mounted in, a iixedrelationship al-,

thoughgrelative ambulatory movement yis producedzbetween,;the..Pattern-cutter,pair and the Work-tracer pair as, wellmas arelativemoyement.ofthe pairsin an axial.

direction.` For proper productionof .the desired. nal

contour on the work pieces 47- use .is madefofa patternA which, is of oppositehandor rotatably` phased `180A vdegrees with respect to the position of. the work pieces. sidering ,Figures -`6.an`d 7,. if `the carrier 41. is moving rearwardly, carrying with it the pattern 60, theV reaction of the curved surface104.againStthe tracer finger 62, .pushing `it Vto the left will ,activate .the hydraulic control circuit to cause a movement ofthempattern, the .spindle carrier 41 andthe cutters 46. towardthe right, thereby producing the surface 103 on.the.work piece. Correspondingly, when the. front corner. of the pattern has traversed by the tracer, and the pattern is comingY forward direction from thatof the relatvemovement between the-.pattern60 and` tracer tlingercontact 62 and that the., pattern must thereforebe properly designed andl mounted in correct phasedv relation to the work piece according to the particular contour to be reproduced.

Itlwill further be noted that the work .pieces are shown formed witha taper in an upwardly direction while the pattern -is inverted totaper in a downward direction. Byl

this relationship, as the slide 41 is adjusted toward or from the work supportthe relativel movement of parts 60-627 and 46+-4Z will be equalbut opposite so that the respective axially transverse -planes of contour engagement between tracer and .pattern on the one hand and cutter and work on- For effective reproduction,l therefore,`

Con-

the other will correspond as to axially related dimensions either from base or apex of the pattern and work.

What is claimed is:

l. A contour grinding machine including a bed having a work supporting portion, a column rising from the bed, a slide mounted on the column for movement toward and from the bed, a spindle carrier, a parallel motion connection between the slide and the spindle carrier comprising spaced toggle mechanisms each including a link pivoted to the carrier, a link pivoted to the slide, means pivotally connecting the links of each toggle, the links pivoted to the carrier being parallel and the links pivoted to the slide being parallel and a tie rod joining the connecting pivots of the respective toggles for maintaining same in prescribed relation one to the other, said toggles suspending the carrier on the slide, a first power means interconnecting the slide and carrier actuable for controlling their relative spacing, and a second power means interconnecting the slide and carrier and activatable to effect relative longitudinal movement of the slide and carrier.

2. A contour grinding machine including a bed having a work supporting portion, a column rising from the bed. a slide mounted on the column for movement toward and from the bed, a spindle carrier, a parallel motion connection between the slide and the spindle carrier comprising spaced toggle mechanisms each including a link Apivoted to the carrier, a link pivoted to the slide, means pivotally connecting the links of each toggle, the links pivoted to the carrier being parallel and the links pivoted to the slide being parallel and a tie rod joining the connecting pivots of the respective toggles for maintaining same in prescribed relation one to the other, said toggle suspending the carrier on the slide, a first power means interconnecting the slide and carrier actuable for controlling their relative spacing, a second power' means interconnecting the slide and carrier and activatable to effect relative longitudinal movement of the slide and carrier, said rst power means including a hydraulic motor supported on the slide having a reciprocating piston, a rod projecting from the piston in the direction of the carrier, and means on the carrier providing a longitudinal guideway, the

piston rod having a portion interlocking with the guideway and reacting through said means on the carrier to eiiect in and out movement of the carrier.

3. A contour grinding machine including a bed having a work supporting portion, a column rising from the bed, a slide mounted on the column for movement toward and from the bed, a spindle carrier, a parallel motion connection between the slide and the spindle carrier comf prising spaced toggle mechanisms each including a link pivoted. to the canier, a link pivoted to the slide, means pivotally connecting the links of each toggle, the links piveted to the carrier being parallel and the links pivoted to the slide being parallel and a tie rod joining the connectingr pivots of the respective toggles for maintaining same in prescribed relation one to the other, said toggles suspending the carrier on the slide, a first power means interconnecting the slide and carrier actuable for controlling their relative spacing, a second power means interconnecting the slide and carrier and activatable to effect relative longitudinal movement of the slide and carrier. said power means for controlling the relative longitudinal movement of the slide and carrier comprising a hydraulic motor on the slide including a piston having a piston rnd reciprocable in a direction parallel to the tie rod, means on the carrier providing ways extending at right angles to the direction of extent of the piston rod, and means on the rod interengaged with said ways for transmitting movements of the rod to the carrier.

4. A contour grinding machine including a bed having a work supporting portion, a column rising from the bed. a siide mounted on the column for movement toward and from the bed, a spindle carrier, a parallel motion connection between the slide and the spindle carrier comprising spaced toggle mechanisms each including a link pivoted to the carrier, a link pivoted to the slide. means pivotally connecting the links of each toggle, the links pivoted to the carrier being parallel and the links pivoted to the slide being parallel and a tie rod joining the connectingipivots of the respective toggles for maintaining same in prescribed relation one to the other, said toggles suspending the carrier on the slide for movement toward and from and for longitudinal movement parallel with the slide, a first power means interconnecting the slide and carrier actuable for controlling their relative spac-v ing, a second power means interconnecting the slide and carrier and activatable to effect relative longitudinal movement of the slide and carrier, said first power means including a hydraulic motor supported on the slide having a reciprocating piston, a rod projecting from the piston in the direction of the carrier, means on the carrier providing a longitudinal guideway, the piston rod having a portion interlocking with the guideway and reacting through said means on the carrier to effect in and out movement of the carrier, and said power means for controlling the relative longitudinal movement of the siide and carrier comprising a hydraulic motor on the slide including a pistonhaving a piston rod reciprocable in a direction parallel to the tie rod, means on the carrier providing ways extending at right angles to the direction of extent of the piston rod, and means on the rod Vinterengaged with said ways for transmitting movements of the rod to the carrier.

5. A contour grinding machine including a bed having a work supporting portion, a column rising from the bed, a slide mounted on the column for movement toward and from the bed, a spindle carrier, a parallel motion connection between the slide and the spindle carrier comprising spaced toggle mechanisms each including a link pivoted to the carrier, a link pivoted to the slide, means pivotaliy connecting the links of each toggle, the links pivoted to the carrier being parallel and the links pivoted to the slide being parallel and a tie rod joining the connecting pivots ot the respective toggles for maintaining same in prescribed relation one to the other, said togglesl .suspending the carrier on the slide for movement toward and from and for longitudinal movement parallel with the slide, a rst power means interconnecting the slide and carrier actuable for controlling their relative spacing, a, second power means interconnecting the slide and carrier and activatable to eiiect relative transverse movement ot the slide and carrier, said first power means including a hydraulic motor supported on the slide having a reciprocating piston, a rod projecting from the piston in the direction of the carrier, means on the carrier providing a longitudinal guideway, the piston rod having a portion interlocking with the guideway and reacting through said means on the carrier to effect in and out movement of the carrier, and said power means for controlling the relative longitudinal movement of the slide and carrier comprising a hydraulic motor on the .slide including a piston having a piston rod reciprocable in a direction parallel to the tie rod, means on the cartier providing ways extending at right angles to the direction of extent of the piston rod, means on the rod interengaged with said ways for transmitting movements of the rod to the carrier, a pattern supported on the spindle carrier, and a contouring tracer control mechanism carried by the bed adjacent the work supporting portion of the bed, said mechanism including a control finger extending in the direction of the pattern support for actuation by a pattern on the support automatically to control the directional movements of the spindle carrier.

6. A contour grinding machine including a bed having a work supporting portion, a column rising from the bed. a slide mounted on the column for movement toward and from the bed, a spindle carrier, a parallel motion connection between the slide and the spindle carrier including spaced toggle mechanisms each including a link pivoted to the carrier, a link pivoted to the slide, means pivotally connecting the links of each toggle the links pivoted to the carrier being parallel and the links pivoted to the slide being parallel and a tie rod joining the connecting pivots of the respective toggles for maintaining same in prescribed relation one to the other, said toggles suspending the carrier on the slide, a first means conneet-ing the slide and carrier to maintain them in spaced relation while permitting their relative longitudinal movement. and a second means connecting the slide and carrier to prevent their longitudinal movement while permitting their relative toward and from movement, and a power device for adjusting one of said means to vary the relative positions of the slide and carrier.

7. A contour grindingmachine including a bed having a work supporting portion, a column rising from the bed. a slide mounted on the column for movement toward and from the bed, a spindle carrier, a parallel motion connection between the slide and the spindle carrier including spaced toggle mechanisms each including a link1 pivotal rto :the: carrier, `a link pivoted tor the slide, meansrpivotally connecting :the-links Aof eachftoggle, the links pivoted ,tothe` carrier being parallel and Vthe links pivotedto the slidebeingy parallelA and a tie rod joining the connectingpivots l of the respective toggles for maintaining same in prescribed relation one to the other, said toggles suspending thecarrier onlthe slide, a rst means connecting theslidefand/carrier to maintain them in spaced 'relation While permitting their relative longitudinal movement, and a secondmeans connecting the slide and carrier-to prevent their longitudinal movement while permittingtheirrelative toward and from movement, a first powerdevicefor adjusting one of said means. a second power device'for adjusting the other of said means, and a commomcontroller for determining the actuation of both power devices to establish the resultant direction of movement of theztoggle suspended carrier with respect to the slide.-y

8. A contour grinding machine including a bed having a work supporting portion; acolumn rising from the bed, a slide mounted on-the column-for movement toward and fromthe bed, a spindle carrier, a parallel motion connection between the slide'andthe spindle carrier including spaced toggle mechanisms each including a link pivoted to the lcarrierya link pivoted to .the slide, means pivotally connecting the `links of eachl toggle, the links pivoted to the carrier being parallel and the links pivoted to the slide being-parallel andatie rod joining the connecting pivots of `the, respectivetoggles forfmaintaining same iny prescribed yrelationwone to the other, said toggles suspending the :carrieron the slide', a rst means connecting the slideand carrier vto'maintain. them in spaced relation while permitting their relative longitudinal movement, and a second means connecting the slide and carrier to preventtheir longitudinal movement while permitting their relative toward iand frommovement, a first power devicevfor adjusting one of said means, a second power device for adjusting ;the other,of said means, and a common controllerfor determiningthe actuation of both power devicesto establishthe resultant direction of 40 movement of the :toggle suspended carrier with respect to the slide, saidcontroller includinga tracer unit carriedtbyithebedrhaving a-patternfcontactor finger projecting towardathe,carrierffor Aactuationtby a pattern on the carrier, automatically to establishsaid resultant direction of'movement.

9. A-contour grinding machine including a .bed having'a work supporting portion, a column rising from the bed, a slide .mountedon the column for movement toward `and'fr,orr1;the.xbed, a spindlecarrier, a parallel motion connectionbetween the slide and the spindle carrier comprising spaced toggle mechanisms each including a link pivoted to the-"carrier, a1link pivoted to the slide, means pivotally connecting the links of each toggle, the links pivoted to thev carrier being parallel andthe links pivoted to the slide being parallel and a tie rod joining the connecting pivots of the respective toggles for maintaining same` in:.;prescribed :relation onetto the other,

said `toggles, suspending tthe carrier on the slide, a firstv power means interconnecting the slide and carrier actuable for controllingthelr. relative spac1ng,.a second power t means interconnecting the `slide and carrier and activatable to effect relative longitudinal movement of the slide und carrier, and vmeans supporting said slide and carrier for movement relative `to the column, said means comprising a ilexibleV cable, a counterweight intermediately suspended'on the =cable,;pulleys ,carried by the column and supporting the :cable,^ means connecting one end of the cable -to thefsllde', and means connecting the other end of the cabletothe carrier.

References Citedin the le of this patent UNITED STATES PATENTS Number` Name Date 768,917 Streich Aug.l 30, 1904 1,755,967 Pagani Apr. 22, 1930 1,999,853 Anderson Apr. 30, 1935 2,239,625 Roehrn; Apr. 22, 1941 FOREIGN PATENTS Number Country Date 598,924.- Great-Britaim Mar. l, 1948 673,976' Great Britain lune 18, 1952 

